Dunkirk 95M-200 Parameter Manual page 10

SPACE HEATING DIFFERENTIALS (PARAMETERS
22 AND 23)
• The term "differential" is also referred to as
"hysteresis."
• Parameter 22 is the "On" differential. The water
temperature must be at least Parameter 22 less
than the calculated setpoint temperature for the
boiler to turn on.
• Parameter 23 is the "Off" differential. When the
boiler is firing, the water temperature must rise at
least Parameter 23 above the calculated setpoint
temperature for the boiler to turn off.
• See Figure 4 for an explanation of the "On" and
"Off" differentials of the boiler control. Note that the
FIGURE 4 - PARAMETERS 22 AND 23 (SPEACE HEATING ON AND OFF DIFFERENTIALS (HYSTERESIS))
differentials are greater when a heat call starts or
stops, as shown. The differentials decrease with
time until they equal Parameters 22 and 23.
SETTING "OFF" DIFFERENTIAL (PARAMETER 23)
• The factory default setting for Parameter 23 is 4°
F. This works well for most applications.
• For low mass systems (fan coil), performance can
be improved by increasing Parameter 23. This
compensates for the quicker system temperature
response of low-mass systems.
• When setting Parameter 23, make sure that
Parameter 23 plus Parameter 4 is not over 193° F
to avoid possible nuisance lockouts.
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